The invention relates to a device for inspecting surfaces in the interior of holes, recesses, or the like, where the device comprises a light source for producing a light beam, where the light beam can be focused by imaging optics, where the focused light beam can be deflected onto the surface, and where a sensor device is provided for detecting the reflected light beam.
Surface inspections in the interior of holes, recesses, or the like, in particular of boreholes or small cracks with dimensions in the millimeter range, represent an important task in many fields of technology. High quality and close-tolerance bore holes are frequently needed when they are provided to receive movable parts such as pins, cylinders, or small pistons, e.g. in pressure valves. Pressure valves are used in pneumatics but also in other fields such as in automobile technology for fuel injection. There in the meantime, test pins for electrical circuits with pneumatic cylinders with a diameter of 2 mm are finding application. These very small cylinders are necessary in order to keep up with electrical circuits which are constantly getting smaller. Close-tolerance bore holes are also required for shrink connections, where said bore holes cannot be allowed to be subject to damage due to burrs or bubbles. Moreover, it can also be of importance in holes outside of the millimeter range to know the surface quality precisely. Thus, for example, brake cylinders in a motor vehicle must have a particularly high-quality surface since small chips or burrs in the cylinders can lead to the destruction of the parts after even a short time.
For the inspection of surfaces, essentially two processes are used in practice at present. In one system a glass wedge forms optics with which nearly 360° of the surrounding surface can be imaged on a light wave guide bundle. The light wave guide bundle frequently comprises several thousand individual fibers which together conduct an image to a camera. By suitable image processing, structures on the surface can be recognized thereby. However, their actual size, in particular their three-dimensional extension, cannot be determined.
In another technology customary in practice, a monochromatic light beam is deflected onto the surface to be examined, where this light beam is always kept focused on the surface. If the distance between the optics and the illuminated image point changes as a consequence of unevenness of the surface and thus the light beam is no longer focused, then an automatic focusing circuit adjusts the optics in such a manner that the light beam is once again focused on the surface. Via this correction of the optics, the change in distance can be detected. In this way the surface can indeed be measured in three dimensions, but due to the necessary tracking of the focusing only relatively slow measurement speeds can be achieved. An inspection in a running production process thus cannot be realized.
The present invention is thus based on the objective of developing and extending a device of the type stated in the introduction in such a manner that, as far as possible, a rapid, simple, and reproducible inspection of surfaces in the interior of holes, recesses, or the like is possible with dimensioning up into the millimeter range and with the simplest construction. Furthermore, a corresponding process will be specified.